A Russian airliner has crashed in central Sinai with more than 200 people on board, the office of Egypt's prime minister has confirmed.
The Airbus A-321 had just left the Red Sea resort of Sharm El-Sheikh, bound for the Russian city of St Petersburg.
Wreckage of the plane has been found in the Hassana area and bodies removed. An official described a "tragic scene".
Flight KGL9268 disappeared from radar screens when travelling at 9,500m (31,000ft), Egyptian officials said.
Egyptian officials said all the passengers were Russian.
Russian President Vladimir Putin has ordered an official investigation into the crash, and for rescue teams to be sent to the crash site.
A criminal case has also been opened against the airline, Kogalymavia, for "violation of rules of flight and preparation for them", Russia's Ria news agency reported.
The airline, based in western Siberia, operates under the name Metrojet.
Russian authorities say it was carrying 217 passengers, 17 of them children aged between 2 and 17, and seven crew. Most were tourists.
A centre to help relatives of the passengers has been set up at Pulkovo airport, Tass news agency quoted St Petersburg city officials as saying.
Sudden altitude lossInitially there were conflicting reports about the fate of the plane, some suggesting it had disappeared over Cyprus.
But the office of Egyptian Prime Minister Sharif Ismail confirmed in a statement that a "Russian civilian plane... crashed in the central Sinai".
It added that Mr Ismail had formed a crisis committee to deal with the crash.
Media reports say at least 50 ambulances have been sent to the scene.
Access to the area is strictly controlled by the military and the terrain is difficult, correspondents say.
One official told Reuters news agency that at least 100 bodies had been found.
"I now see a tragic scene," the official said. "A lot of dead on the ground and many died whilst strapped to their seats."
The plane split in two, with one part burning up and the other crashing into a rock, he added.
The Russian aviation authority Rosaviatsiya said in a statement that flight KGL9268 left Sharm el-Sheikh at 06:51 Moscow time (03:51 GMT) and had been due into St Petersburg's Pulkovo airport at 12:10.
The authority added that the aircraft failed to make scheduled contact with Cyprus air traffic control 23 minutes after take-off and disappeared from the radar.
Egypt's civilian aviation ministry said the plane had been at an altitude of 9,500m (31,000ft) when it disappeared.
Live flight tracking service Flight Radar 24's Mikail Robertson confirmed the altitude.
He told the BBC that the plane started to drop very fast, losing 1,500m in one minute before coverage was lost.
The BBC's Orla Guerin in Cairo says it is likely there will be speculation about militant involvement in the incident - Sinai has an active militant network, with local Jihadis who have allied themselves to so-called Islamic State.
But the aircraft's altitude suggests that it could not have been struck from the ground, she adds.
An official investigating the crash quoted by al-Ahram newspaper said it was caused by a "technical failure".
Local weather observations in the vicinity of the rescue scene suggest relatively benign conditions.